1. Field of the Invention
The present invention relates to a semiconductor apparatus comprising a circuit composed of a device as typified by a thin film transistor (hereinafter, TFT) that is formed by means of bonding a release layer to a substrate to be transferred thereto and a method for manufacturing the semiconductor apparatus. The present invention relates, for example, to an electrooptical device such as a liquid crystal module, a light emitting apparatus such as an EL module, and an electric appliance installed with such apparatus as its components. In addition, the present invention relates to a peeling method of a device and transferring method of the device to a plastic substrate.
As used herein, the term “semiconductor device” refers to any device as a whole that operates by utilizing semiconductor characteristics. An electrooptical device, a light emitting apparatus, a semiconductor circuit, and an electric appliance are all included in the semiconductor device.
2. Description of the Related Art
Recently, attention has been paid to technology of composing a thin film transistor (TFT) using a semiconductor thin film (the thickness of about several to several hundreds nm) formed on a substrate having an insulating surface. The thin film transistor is widely applied to electronic devices such as IC, an electrooptical device, or the like. Especially, the development of the thin film transistor as a switching element for an image display apparatus has been quickened.
A variety of applications of such an image display apparatus have been expected, above all, utilization of the image display apparatus for mobile devices draws attention. Although a glass substrate, a quartz substrate, or the like is used in many image display apparatuses at present, it has disadvantages that they are easy to crack and heavy. Further, the glass substrate, the quartz substrate, or the like is unsuitable for mass production since it is difficult to be enlarged. Therefore, a TFT device has been attempted to be formed over a substrate having flexibility as typified by a flexible plastic film.
However, since the heat resistance of the plastic film is low, the highest temperature during process is required to be low, consequently, it is impossible at present to form the TFT that has high electric characteristics compared with the one being formed over a glass substrate. Hence, no high-performance liquid crystal display apparatus and light-emitting device using a plastic film has been realized.
If a light-emitting apparatus or a liquid crystal display device in which organic light-emitting device (OLED) is formed on a flexible substrate such as a plastic film or the like can be manufactured, the light-emitting apparatus or the liquid crystal display apparatus can be manufactured to have a thin thickness and light-weight and applied to a curved surface display, a show window, or the like. Thus, its utilization is not limited to a cellular phone and its application range is extremely wide.
However, in general, a substrate formed of plastic penetrates easily moisture or oxygen. An organic light-emitting layer is deteriorated due to these impurities, so that lifetime of a light-emitting apparatus becomes reduced. Therefore, moisture or oxygen is prevented from penetrating into the organic light-emitting layer by interposing an insulating film such as a silicon nitride, silicon oxynitride, or the like between the plastic substrate and an organic light-emitting device conventionally.
In addition, a substrate such as plastic films or the like is weak against heat generally. In case of increasing the deposition temperature for an insulating film such as silicon nitride, silicon nitroxide, or the like, a substrate becomes easily deformed. Further, too low deposition temperature causes decline in quality of the film and difficulty of preventing penetration of moisture or oxygen into a light-emitting device. There is also a problem of deforming and deterioration of a part of a substrate due to localized heat generation during driving of the device that is formed over a substrate such as plastic films or the like.